Microptila nakama sp. nov.

(Figs 3, 4 C, 5)

Diagnosis. The male of this species shows some similarities to Microptila pasak Wells 1993, described from Bali, Indonesia, in having the subgenital plate bilobed distally, these lobes divergent, and a short apical or subapical process on each inferior appendage, but is distinguished from that species as follows: (1) Segment IX with rounded posterolateral angles (Fig. 3 A, cf, IX with digitiform lobes laterally in M. pasak); (2) the caudal excavation of the subgenital plate is narrow and deep (Fig. 3 B, 3D, cf, the excavation wide and shallow in M. pasak); and (3) the inferior appendages each have a short mesal process subapically (Figs. 3 A,3C,3E, cf. the inferior appendages each have a peg-like process at the mesal-caudal corner in M. pasak).

Male. Length of each forewing and hind wing 1.4–1.6 mm and 1.2 mm, respectively (n = 2). Antennae 18–19- segmented and 0.6 mm long (n = 2).

Genitalia (Figs. 3 A–3F). Segment IX (IX) annular, in dorsal view (Fig. 3 B) excavation of anterior margin deep and semi-circular, excavation of posterior margin deep and quadrate, transverse tegmental bridge broad, dorsal midline about 1/5 as long as segment IX; in ventral view (Fig. 3 C) excavation of anterior margin shallow and semicircular, excavation of posterior margin shallow and quadrate. Tergite X (t X) quadrate, in dorsal view (Fig. 3 B) with subquadrate excavation caudally, semimembranous and transparent with lateral margins lightly sclerotized. Subgenital plate (sg plate) large, strongly sclerotized, margins of basal half rounded laterally, distally bilobed, lobes slightly divergent (Figs. 3 B, 3D); in lateral view (Fig. 3 A) stout, rod-shaped, slightly curved ventrad. Inferior appendages (inf app) large, setose; in lateral view (Fig. 3 A) main article stout at basal 4/5 and strongly tapered in apical 1/5; in ventral view (Fig. 3 C) apices incurved, in ventral and ventromesal views (Fig. 3 C, 3E) blunt mesal process subapically. Phallus long, slender, titillator (ti) arising at apical 1/3, encircling phallus 1.5 times (Fig. 3 F).

Female. Unknown.

Holotype: male, Japan, Ryukyu Islands, Iriomote-jima, Nakama-gawa river system, Nishi-funatsuki-gawa, Nishi-funatsuki-bashi, 24˚18’10” N, 123˚51’34” E, 10 m a.s.l., 30.x.2012, T. Ito (CBM-ZI 151363).

Paratype: 1 male, same data as holotype (CBM-ZI 151364).

Etymology. The specific name ( nakama, a noun) refers to the river where this species was collected.

Habitat (Fig. 4 C). Adults of this species were collected from a fast-flowing stream with large boulders.

Distribution (Fig. 5). Japan (Ryukyu Islands: Iriomote-jima). Known only from the type locality.

Japanese name. Nakama-mikuro-himetobikera.